WO2009109211A1

WO2009109211A1 - Controlling an electrically actuatable parking brake in the event of failure of a speed signal

Info

Publication number: WO2009109211A1
Application number: PCT/EP2008/010542
Authority: WO
Inventors: Ralf Kinder; Andreas MÜLLER
Original assignee: Lucas Automotive Gmbh
Priority date: 2008-03-04
Filing date: 2008-12-11
Publication date: 2009-09-11
Also published as: EP2250055A1; CN101970268A; EP2250055B2; EP2250055B1; US20110004386A1; DE102008012387A1; ATE517003T1; CN101970268B; US9221446B2

Abstract

The invention relates to a procedure for controlling an electrically actuatable parking brake of a motor vehicle in the event of the failure of a first signal indicating the speed of said vehicle. The procedure comprises the following steps: the parking brake is continuously closed as long as a second signal (110) indicating the driver's intention to close the parking brake is detected; and the parking brake is opened if said brake is already partially open as long as no second signal is detected (110).

Description

Control of an electrically actuated parking brake in case of failure of a speed signal

Technical area

The invention relates generally to motor vehicle brake systems. In particular, the invention relates to a control of a parking brake in case of failure of a speed signal.

background

Modern motor vehicles have several independent braking systems. A first brake system is usually designed as a service brake and may include additional systems that provide driving stability of the

Improve motor vehicle during braking, for example, ABS, ESP or anti-slip Verge. A second brake system is usually designed primarily for parking braking, so holding the motor vehicle at a standstill. For safety reasons, it is required that a parking brake also be used to bring a moving motor vehicle to a standstill, for example, when the service brake fails or is only partially functional. In addition, electrically operable parking brake systems can assist a driver in stopping or starting the motor vehicle on an uphill or downhill slope.

In order to control an electrically actuated parking brake in different ways, depending on whether the moving motor vehicle is decelerated in a "dynamic mode" of the parking brake or the stationary motor vehicle is to be kept in a "static mode" of the parking brake at standstill, a signal is processed which is at a speed of

Motor vehicle points. On the basis of this signal, a driver-controlled signal for opening or closing the parking brake can then be converted into a suitable activation of actuators of the parking brake as required. For reasons of safety, it is required that a parking brake must still be usable even in the event of a failure of such a speed signal, to decelerate the motor vehicle and to keep it at a standstill. European Patent EP 1 610 991 B1 proposes for this purpose to bring an electric parking brake into a partially closed state in the event of failure of the speed signal and activation by a driver in a first step. After a predetermined time, the parking brake is then transferred in a second step from the partially closed state abruptly in a fully closed state. The proposed approach is based on the assumption that the motor vehicle, if it had been moving during the first step, has come to a standstill before the second step.

In some situations, however, this assumption does not apply, for example, when braking from high speed or during a long downhill ride, and the driving stability of the motor vehicle may be jeopardized by the sudden complete closing of the parking brake. If the parking brake of the still moving motor vehicle is suddenly completely closed, then it is possible for one or more of the wheels of the motor vehicle to block, thereby impairing a driving stability of the motor vehicle.

The invention has for its object to resolve the above-mentioned disadvantages in case of failure of a speed signal at a parking brake.

Short outline

According to a first aspect, a method is provided for controlling an electrically actuable parking brake of a motor vehicle in the event of failure of a first signal indicative of a speed of the motor vehicle, comprising the steps of continuously closing the parking brake as long as the parking brake is at a driver's request. indicative second signal is detected, and the opening of the parking brake, when a failure of the second signal is detected, if the parking brake is in a partially open state comprises.

The first signal may be, for example, a wheel speed signal or a signal formed from a plurality of wheel speed signals; Alternatively or additionally, the first signal can also be formed on the basis of a signal of a gyrator or a navigation system, for example. The second signal can be, for example, an electrical signal which a driver of the motor vehicle generates by means of an electrical push-button or switch. The method may include fully opening the parking brake if the second signal is not (re) detected during opening. In this way, by not generating the second signal, the driver can completely release the parking brake again, or he can regenerate the second signal during release and thereby close the parking brake again. A second signal generated by the driver in rapid succession and not generated may hold the parking brake in an associated region of an open state.

The continuous closure does not include jumps affecting drivability and may include continuous closing with a limited closing speed. In one variant, the limited closing speed is below a maximum achievable by the control closing speed. The continuous closing may also include not maintaining a partially opened state of the parking brake for a certain period of time, that is, not taking a break during the closing operation.

The closing speed can be constant. In this case, a linear closing of the parking brake can take place. The closing speed curve can but z. B. also change linearly, for example linearly rising or falling linearly. In this case, the parking brake can be closed progressively or vice versa. For example, a closing speed may be expressed in terms of a course of a closing path, a closing force, or a closing pressure over a period of time.

The method may further include holding the parking brake in a fully-closed state, provided that the parking brake is in the fully closed state in the absence of the second signal. In this way, the parking brake can be brought into a closed, locked state in which it secures, for example, a stationary motor vehicle against unintentional rolling away.

The method may further include opening the parking brake in a fully-closed state in the presence of a third signal indicative of a driver request to open the parking brake. This third signal may be identical to or derived from the second signal. The parking brake may include a plurality of groups of actuators, and the closing of the parking brake may include increasing the braking force of the actuators of at least one first group and maintaining the braking force of the actuators of at least one second group. As a result, if a maximum of a μ-slip curve is exceeded by one or more wheels, the wheel or those wheels whose actuators have not been further closed, cornering forces continue to be transmitted. Each of the groups may include one or more actuators. In one embodiment, the first group comprises a plurality of actuators, which are associated with a front axle of the motor vehicle, and the second group comprises a plurality of actuators, which are associated with a rear axle of the motor vehicle. In a further embodiment, each group comprises respective actuators, which are associated with each other diagonally opposite wheels of the motor vehicle.

The method may further include determining a state of motion of the motor vehicle based on the first signal. The movement state may include a speed and / or a direction of movement of the motor vehicle. The direction of movement may designate a forward / reverse travel of the motor vehicle and / or an absolute direction of movement of the motor vehicle. In particular, the state of motion can indicate a standstill of the motor vehicle.

If the motor vehicle is at a standstill, the method may further include fully closing the parking brake when at least temporarily detecting the second signal. For example, the driver can ensure that the parking brake is closed and the motor vehicle is kept at a standstill, for example by briefly pressing a button or switch that generates the second signal.

When the motor vehicle is in motion, the method may further include moving the parking brake to a partially closed state when the second signal is detected and opening the parking brake in the absence of the second signal. The partially closed state can be defined, for example, by a closing path, a closing time, a closing force or a closing pressure. If a movement of the vehicle is reliably detected, it is possible in this way, for example by means of the parking brake, to apply a predetermined braking force to the vehicle

Motor vehicle are exercised, as long as the driver holds a button pressed. Leaves he loses the button while the motor vehicle is still moving, the parking brake is released again.

According to a second aspect, a computer program product with 5 program code means for carrying out the method described above is provided when the computer program product runs on a processing unit. Such a processing unit may be a control unit on or in the motor vehicle. The processing unit may also control other functions of the motor vehicle, such as braking functions such as ABS, lo ESP or hill start help.

The computer program product may be stored on a computer-readable medium. For example, the computer program product may be stored on a removable medium such as a floppy disk, hard disk, i5 CD, WORM or DVD, or on a fixed medium such as a semiconductor memory (such as a RAM, ROM, EPROM, EEPROM, NOVRAM or Flash).

According to a third aspect, a control device for an electrically operable 2o parking brake of a motor vehicle in case of failure of a on a

Speed of the motor vehicle indicative first signal is provided, which comprises a first determination means for determining a failure of a pointing to a speed of the motor vehicle first signal, a detection means for detecting a close to a driver's request, the parking brake indicative second signal, a second

Determining means for determining a partially opened state of the parking brake, a closing means for continuously closing the parking brake as long as the second signal is present, and an opening means for opening the parking brake when the second signal is absent, provided that the 3o parking brake is in a partially open state.

The first determining means may determine a failure of the first signal based on processing one or more sensor signals. Alternatively or additionally, a failure can be determined in the absence of plausibility of sensor signals 35 or combinations thereof. The detection device may include, for example, a switch or a button. The second determination device may, for example, be one in conjunction with an actuator arranged sensor include. Such a sensor may, for example, sense a path, time, force or pressure indicative of an opening condition of the actuator. The locking device may comprise a control for the electrically actuated parking brake. In particular, it may include a drive for one or more actuators. The opening device can be constructed analogously to the closing device or designed to be integrated with it.

The control device may comprise a third determination device for determining a movement state of the motor vehicle. The third lo determination device may, for example, be connected to the same signal sources as the first determination device.

The parking brake may include a plurality of groups of actuators, and the opening and closing means of the control device may be configured to independently actuate the actuators of at least two groups. Each of the groups may include one or more actuators and each actuator may include a latch for holding a condition.

20 Brief description of the drawings

Further features and advantages of the invention will now be described in connection with an embodiment and the accompanying drawings, in which:

FIG. 1 shows a schematic overview of an electrically actuated parking brake of a motor vehicle; FIG.

Fig. 2 shows a schematic representation of a control device according to Fig. 1;

Fig. 3 is a schematic flow diagram of a method of controlling a parking brake of Fig. 1; and

FIGS. 4 a and b show different courses of opening states of a parking brake and driver-controlled signals.

35

In the figures, matching elements bear the same reference numerals. Description of a preferred embodiment

Fig. 1 shows an embodiment of an electrically actuated parking brake 100 of a motor vehicle. The parking brake 100 comprises a processing unit 5 120 which has an input for an opening / closing signal 110 and is connected to actuators 130, 140, 150 and 160. In addition, the processing unit 120 has an input for a speed signal 170. The opening / closing signal 110 is generated by a driver of the motor vehicle and signals a driver's request to open or close the parking brake.

10

In the embodiment shown in FIG. 1, the motor vehicle is a truck with two rear axles. Each of the two rear axles are each associated with two wheel brakes, and each wheel brake is in turn assigned to one of the actuators 130 to 160. Two actuators i5 each form an actuator group. The two actuators of a

Actuator group of the same rear axle or different rear axles be assigned.

Notwithstanding the described embodiment, the teaching described here can also be implemented in a motor vehicle which has only one rear axle. In such a case, then two of the actuators of the front axle and the other two actuators would be assigned to the rear axle. According to a further variant, only two actuators are provided and assigned to the (eg single) rear axle. This variant corresponds to the usual construction of a car parking brake system which acts exclusively on the rear axle.

The processing unit 120 is configured to open, close or hold in a state the actuators 130 to 160 shown in FIG. 1 in groups. It controls the actuators 130 to 160 in response to the opening / closing signal

3o 110 and a speed signal 170. If the speed signal 170 is present, a driving state and a standstill of the motor vehicle can be reliably detected. Depending on the opening / closing signal 110, the actuators 130 to 160 may then be controlled in a static mode according to a deceleration of the motor vehicle in a dynamic mode of the parking brake 100 or a stop of the motor vehicle 5 at a standstill. FIG. 2 shows a schematic representation of a control device 200 for the electrically actuatable parking brake 100 from FIG. 1. The control device 200 includes the processing unit 120 shown in FIG. 1. The processing unit 120 comprises a microcomputer 210, which is provided with determination units 220, 230, 240, 250 and 270 and connected to a drive 260.

The determination unit 220 is configured to detect a closing signal 280 and to signal the microcomputer 210 of the presence of a driver request to close the parking brake. In a corresponding manner, the determination unit 230 detects an opening signal 290 and signals the microcomputer 210 that there is a driver request to open the parking brake. Each of the signals 280 and 290 may be generated by a dedicated button or switch (not shown). Alternatively, the opening signal 280 and the closing signal 290 may be combined as the opening / closing signal 110. In this case, the opening

/ Closing signal 110, for example, by a single button (not shown) are generated. Pressing the button or switch then generates an opening or closing signal (alternately or depending on the situation). The determining means 220 and 230 may be implemented in this case as an integrated unit.

In an alternative embodiment, to generate the signals 280 and 290, a three-position switch (not shown) may be used, for example in a first position the opening signal (290), in a second position no signal and in a third position the Closed signal (290) generated. In this way, the opening and closing signals can be mutually exclusive.

The determination units 240 and 250 are configured to evaluate the speed signal 170. The determining unit 240 signals to the microcomputer 210 a failure of the speed signal 170, while the determining unit 250 determines a moving state of the motor vehicle based on the speed signal 170 (and possibly other signals, not shown) and provides it to the microcomputer 210.

The microcomputer 210 controls the actuators 130-160 by means of the driving device 260 in such a way that they are opened, closed or held in their state. For the sake of clarity, only a control device 290 and one of the actuators 130-160 are represented in FIG However, a plurality of actuators are controlled individually or in groups, as stated above with reference to FIG. 1. The driver 260 may drive each of the actuators 130-160, for example, by pulse width modulation, current or voltage control or any other known manner.

5

The determination device 270 evaluates an opening signal 295 of one of the actuators 130 to 160 and signals the microcomputer 210 an opening state of the actuator. The opening signal may be, for example, a rotary signal of an electric motor or a time, path, pressure or force signal. In other embodiments, the determination device 280 can determine the opening state, for example, from a time profile of a current or a voltage, wherein corresponding values can be sampled, for example, at the actuator or at the drive device 290.

FIG. 3 shows a schematic flow diagram 300 of a method for controlling the electrically actuatable parking brake 100 according to FIG. 1. For the sake of clarity, only the control of the actuator 130 will be described as an example.

Starting from a start state 305, it is determined in a first step 310 whether there is a speed signal (v signal) 170 or not. An absence of the speed signal 170 can also be determined if a signal indicative of a speed of the motor vehicle is detected as being implausible or undefined. If an absence of the speed signal 170 is determined in step 310, it is then checked in a step 315 25 whether the actuated actuator 130 is completely closed. If this is not the case, it is checked in a step 320 whether the closing signal 280 is present or not. As stated above, the closing signal 280 may be identical to the opening signal 290 and may be present as a combined opening / closing signal 110. If the closing signal 280 is present, then the actuator 130 is closed continuously (ie braking force jumps impairing driving stability) in a subsequent step 325 as long as the closing signal 280 is detected. This process will be described below with reference to Figs. 4a and 4b explained in more detail. The state 330 following the step 325 corresponds to the state 305, so that the method can be carried out anew.

35

On the other hand, if it is determined in step 320 that the closing signal 280 is not present, it is checked in a step 335 whether the actuator 130 is fully opened. If this is the case, the method is again in state 330 (or 305). Otherwise, the actuator 130 is opened in a step 340.

By means of the previously described steps 305 to 340, the motor vehicle can also 5 in the absence of speed signal 170 by the driver by means of

Parking brake 100 are braked without risking an unstable driving condition by instantaneous complete closing of the parking brake 100. Nevertheless, the driver can bring about a fully closed, locked state of the parking brake 100 for holding the motor vehicle at a standstill.

10

If it is determined in step 315 that the parking brake 100 is already fully closed, the presence of the opening signal 290 is checked in a step 345. If there is no opening signal 290, the process goes to state 330 (or 305). Otherwise, the parking brake 100 is first opened in steps i5 335 and 340, as set forth above, if it is not yet fully opened before the method assumes state 330 (or 305).

The steps 350 to 370 of the method 300 described below relate to a control of the parking brake 100 in the presence of the speed signal 20 170.

If it is determined in step 310 that the speed signal 170 is present, a query is subsequently made in a step 350 as to whether the motor vehicle is at a standstill. The motor vehicle is stationary, the parking brake 100 is in a

25 in static mode, in which it is first determined in a step 355 whether a closing signal 280 is present. If the closing signal 280 is present, then the parking brake 100 is completely closed in a step 360 and the static mode is ended before the method is again in the state 330 (or 305). If it is determined in step 355 that there is no closing signal 280, then goes

3o the method in the state 330 (or 305) via. It should be noted that in

Step 360 closing the parking brake 100 is not only as long as the closing signal 280 is present, but that even in the presence of only the closing signal 280, the parking brake 100 is fully closed in step 360.

35

If it is determined in step 350 that the motor vehicle is not at a standstill, the parking brake 100 is operated in a dynamic mode. In this will be First, in a step 365 analogous to step 355 determines whether the closing signal 280 is present. If this is the case, the parking brake 100 is partially closed in a step 360 ^. B. as long as the closing signal 280 is detected). After step 370, the dynamic mode is ended and the method transitions to state 330 (or 305). If it is determined in step 365 that the closing signal 280 is not present (or no longer), the parking brake 100 is opened in steps 335 and 340, as stated above.

FIGS. 4a and 4b show different time profiles 400 and 450 of the closing forces of the parking brake 100 according to FIG. 1 and of an opening / closing signal 110 in the absence of the speed signal 170. In both figures, the horizontal axes denote the time, while the vertical axes denote a closing force F of the parking brake 100 as an exemplary, an opening state of the parking brake 100 indicative size. As stated above, as a measure of an opening state of the parking brake 100, instead of the closing force, for example, a closing path or a hydraulic operating pressure could also be used. A maximum firing force 410, which corresponds to a fully closed state of the parking brake 100, is shown in both FIGS. 4a and 4b as a horizontal, dashed line. For the (e.g., binary) opening / closing signal 110, only its presence is indicated in the vertical direction.

In Fig. 4a is from the time to the opening / closing signal 110 before. After a short delay, from the time ti in response to the opening / closing signal 110, the parking brake 100 is continuously closed and the closing force 420 increases. Even before the closing force 420 reaches the maximum closing force 410, the opening / closing signal 110 drops away again at a time t _2a and the parking brake 100 is subsequently opened again, as shown by the falling closing force 420. At the time t _3a , the parking brake 100 is fully opened and the closing force 420 is again at the value zero.

In Fig. 4b, a different course of a closing force 460 of the parking brake 100 is shown. As in Fig. 4a, the opening / closing signal 110 is present from the time to, and from the time ti follows a continuous closing of the parking brake 100, so that the closing force 460 is continuously increased. When, at a time t _2b, the closing force 460 reaches the maximum closing force 410, the opening / closing signal 110 is still present. At the time t ₂ b, the parking brake 100 is thus completely closed and is kept in the following even in the event of later omission of the opening / closing signal 110 in the fully closed state. The closing force 460 remains constant just above the maximum closing force 410. The slight "overshoot" the closing force 460 on the maximum closing force 410 may, for example, by an overrun of the actuator which drives the electric motor be caused. From the time t falls _3b the opening / closing signal 110 back away.

The closing force 460 remains unlike the situation in Fig. 4a also after the time t ₃ b at its maximum value, since the parking brake, when it has reached a fully closed state, regardless of the lack of opening / closing signal 110 is not opened.

The alternative courses 470 and 480 of the closing force between the times ti and t _2b in FIG. 4 b represent other variants of a continuous closing of the parking brake 100. The course 470 corresponds to a progressive closing of the parking brake, which corresponds to a linearly increasing closing speed. The course 480 represents a reverse progressive course of the closing force, which corresponds to a linearly decreasing closing speed. The associated with the history 460

Closing speed between the times ti and t _2b , however, is constant. From the time t ₂ b, the curves 460, 470 and 480 are identical to each other and it is only the course 460 located. Corresponding progressive and, conversely, progressive courses 470 and 480 are also possible in the situation illustrated in FIG. 4a, but not shown.

In Fig. 4a is shown clearly how a braking force in response to the opening / closing signal 110 continuously and without braking force jumps and dismantled again. The parking brake 100 thereby behaves predictable and controllable for the driver, and an unstable driving condition can be avoided.

In Fig. 4b can be clearly seen how the parking brake 100 is brought into a fully closed state without a "break" would be inserted, as proposed in EP 1 610 991 B1. The driver does not have to wait for the parking brake to lock in the fully-closed state, which reduces the risk of an accidentally unlocked parking brake.

Claims

claims

Anspruch [en] A method (300) for controlling an electrically actuable parking brake (100) of a motor vehicle in the event of failure of a vehicle at a speed of

5 motor vehicle indicative first signal (170), comprising the following steps:

- continuously closing (325) the parking brake (100) as long as a second signal (280) indicative of a driver request to close the parking brake (100) is detected; and lo - opening (340) the parking brake (100) when the second one is absent

Signal (280) is detected, provided that the parking brake (100) is in a partially open state.

The method (300) of claim 1, further comprising fully opening i5 the parking brake (100) if the second signal (280) during opening

(340) is not recorded.

3. The method (300) according to any one of claims 1 or 2, characterized in that the continuous closing (325) is a continuous closing with a

20 limited closing speed includes.

4. The method (300) according to claim 3, characterized in that the closing speed is substantially constant.

5. Method (300) according to claim 3, characterized in that the closing speed changes substantially linearly.

The method (300) of any one of the preceding claims, further comprising maintaining the parking brake (100) in a fully closed state

30 condition, provided that the parking brake (100) in the absence of the second

Signal (280) is in the fully closed state.

The method (300) of any one of the preceding claims, further comprising opening (340) in a fully closed state

35 parking brake (100) in the presence of a driver's request, the

Parking brake open, indicative third signal (290).

The method (300) according to one of the preceding claims, wherein the parking brake (100) comprises a plurality of groups of actuators (130, 140, 150, 160), characterized in that closing (325) of the parking brake (100) increases the parking brake Braking force of the actuators (130, 140,

5 150, 160) of at least a first group and holding the braking force of

Actuators (130, 140, 150, 160) comprises at least a second group.

The method (300) of any of the preceding claims, further comprising determining (350) a state of motion of the motor vehicle based on the first signal (170).

The method (300) of claim 9, wherein the motor vehicle is at a standstill, and further comprising fully closing (360) the parking brake (100) when at least temporarily detecting the second signal i5 (280).

Computer program product with program code means for carrying out a method according to one of the preceding claims, when the computer program product runs on a processing unit (120).

20

12. Computer program product according to the previous claim, when it is stored on a computer-readable medium.

13. Device (120) for controlling an electrically actuated parking brake 25 (100) of a motor vehicle in case of failure of a speed of the

Motor vehicle indicative first signal (170), comprising:

a first determining means (240) for determining a failure of a first signal (170) indicative of a speed of the motor vehicle;

3o - a detection device (220) for detecting one on one

Driver's request to close the parking brake, indicative second signal (280);

- a second determining means (270) for determining a partially opened state of the parking brake (100);

35 - a closing device (260) for continuously closing the

Parking brake (100) as long as the second signal (280) is detected; and

- An opening device (260) for opening the parking brake (100), when the second signal (280) fails, provided that the parking brake (100) is in a partially open state.

14. Device (120) according to claim 13, characterized in that it has a third determination device (250) for determining a

Moving state of the motor vehicle includes.

15. Device (120) according to claim 13, wherein the parking brake (100) comprises a plurality of groups of actuators (130, 140, 150, 160) and the opening and closing devices (260) are formed, the actuators (130 , 140, 150, 160) of at least two groups independently of one another.